Study data published in the American Journal of Psychiatry indicate that substance use disorders (SUDs) significantly increase the risk of mortality in patients with eating disorders. In a national cohort study conducted in Denmark, comorbid SUDs were associated with substantially greater risk of death across eating disorders of all types. Efforts to identify and treat SUDs in patients with eating disorders are urgently needed to reduce excess mortality.
This retrospective cohort study used data from Danish nationwide registers to identify patients diagnosed with an eating disorder between 1994 and 2015. Patients were stratified into 3 categories by disorder subtype: anorexia nervosa, bulimia nervosa, and unspecified eating disorder. The control group comprised of individuals without an eating disorder, identified using the Danish Civil Registration System.
Patients were matched in a 1:4 ratio by age, sex, and ethnicity to control participants. Patients and control subjects were considered to have an SUD if they were diagnosed with an SUD or received treatment for an SUD during follow-up. The primary outcome was mortality, determined using the Cause of Death Register. Cox regression was used to assess all-cause mortality among patients compared with control participants.
The study cohort comprised 20,759 patients with an eating disorder and 83,036 control subjects. The patient and control groups had total follow-up times of 227,538 and 939,628 person-years, respectively. The majority of participants were women (93.2%) and of Danish descent (94.2%). Most individuals were under 30 years of age at enrollment (91.6%).
SUDs were significantly more common in the patient group compared with the control group, with overall prevalence rates of 10.1% and 2.7%, respectively (P <.001). Specifically, patients were significantly more likely than control participants to report alcohol abuse or dependence (4.7% vs 1.0%), cannabis abuse or dependence (3.4% vs 1.3%), and hard drug abuse or dependence (4.7% vs 1.3%) (all P <.001).
Deaths occurred in 1.4% of the patient group and 0.4% of the control group during follow-up (P <.001). Death by suicide comprised a significantly greater proportion of deaths in the patient group vs control group (24.8% vs 14.6%; P <.001).
In regression models, patients with eating disorders alone had an elevated risk for all-cause mortality compared with control participants (hazard ratio [HR], 2.85; 95% confidence interval [CI], 2.40-3.38). The risk of death increased substantially with a comorbid SUD.
Compared with control participants without SUDs, the HRs (95% CI) for all-cause mortality were higher in patients with eating disorders who abused alcohol only (11.84 [8.67-16.16]), cannabis only (4.55 [2.34-8.84]), hard drugs only (14.16 [9.81-20.43]), alcohol and cannabis (4.69 [1.18-18.64]), alcohol and hard drugs (19.59 [12.76-30.09]), cannabis and hard drugs (13.67 [8.22-22.75]), and all 3 substance categories (22.99 [14.64-36.11]). Control participants with SUDs also had elevated risk of mortality compared with control participants without SUDs, though the difference was much less pronounced than among patients with eating disorders.
Risk profiles differed by eating disorder subtype. Compared with control subjects without SUDs, patients with anorexia nervosa and hard drug use had a 20-fold increased risk of death during follow-up (HR, 22.34; 95% CI, 15.13-33.00). Patients with unspecified eating disorder and hard drug abuse had an HR of 15.53 (95% CI, 10.15-23.78) compared with controls. All-cause mortality was not elevated in patients with bulimia nervosa alone, but bulimia nervosa combined with alcohol and/or cannabis abuse (HR, 5.86; 95% CI, 3.37-10.19) and hard drug use (HR, 11.43; 7.14-18.28) was associated with increased risk over control subjects.
These results underscore the health impacts of eating disorders and SUDs, which together appear to have an additive effect on mortality. As study limitations, investigators noted that analyses were not adjusted for tobacco use, which is a known contributor to excess mortality. Even so, the nationwide nature of the analysis, large cohort size, and controlled design strengthen the data generalizability.
“These findings highlight the importance of focusing on the prevention and treatment of SUDs to reduce excess mortality in eating disorder patients,” investigators wrote.
“This is particularly relevant for [anorexia nervosa] patients who abuse hard drugs, since they were found to be the most susceptible to premature death. Interestingly, the driving factor behind mortality in [bulimia nervosa] patients appears to be SUD, and thus the prevention and treatment of SUDs would go a long way toward reducing mortality in [bulimia nervosa].”
Mellentin AI, Mejldal A, Guala MM, et al. The impact of alcohol and other substance use disorders on mortality in patients with eating disorders: a nationwide register-based retrospective cohort study. Am J Psychiatry. Published online October 26, 2021. doi:10.1176/appi.ajp.21030274